Patent GB-787596-A (GB)
Title: An improved mechanism for the production of a variable number of impulses at timed intervals
Inventor: HARDS ERNEST JOHN
IPC: H04M15/10
Filed: 1955-05-13
Abstract: 787,596. Automatic exchange apparatus. SIEMENS EDISON SWAN, Ltd., [formerly SIEMENS BROS. & CO., Ltd.]. May 10, 1956 [May 13, 1955], No. 13877/55. Class 40 (4). A mechanism for producing pulses to control a subscriber's meter in accordance with the character and duration of a call has a number of cam-controlled spring sets amongst which a cam is set from an initial position by a train of impulses applied to a step-by-step motor driving the cams in order to determine the rate of charge, the mechanism being operable at timed intervals to rotate its cams through one revolution to produce metering pulses during that part only of the movement of the cam between its set and initial positions. The mechanism in combination with the call timing device described in Specification 782,019 can meter the first three minutes of a call and meter subsequent one-minute intervals at a reduced rate. Construction of mechanism. As shown in Figs. 1 and 3, the mechanism has spring sets ON, MF, SF, and MON, controlled by cams 19, 21, 22, and 26, respectively. Cam 19 is mounted on a half-shaft 16, and cams 21, 22 are mounted on a half-shaft 20, rotatable on a fixed spindle 17 carried between mounting arms 1 and 2. Cam 26 is carried by a disc 25 housing a planet-wheel 24 which works between sun wheels 18 and 23 on the half-shafts 16 and 20. The disc 25 also carries an armature 29 on a spring arm 31 with a pin 30 projecting through the disc to engage sun-wheel 19 to lock the shafts 16 and 20 together. If an electromagnet 27 mounted on the arm 2 is energized, when the disc 25 is in the position shown, the pin 30 is withdrawn by armature 29 and shafts 16 and 20 rotate in opposite directions. The frame of the mechanism carries an E-shaped motor magnet having two windings on its centre limb, the open ends of the E being spanned by a spring-biased armature 9, Fig. 3, pivotally mounted to carry a V- shaped arm 12 to which is attached a finger 13 engaging a ratchet wheel 14 with 30 teeth mounted on the half-shaft 16. Each time the E-shaped magnet is energized contacts DM are operated by means of arms 34 and 35 engaging the arm 12. The spring set MF may be locked to be independent of its cam 21 by means of an electromagnet 37, the magnet being ineffective until the cam 21 moves an armature 40 connected to an operating post 43 with range of the polepieces of the magnet, see. Fig. 3. Alternatively the spring set may be locked by a mechanically operated latch which can be released electromagnetically. The contours of the cams are shown in their normal positions in Fig. 4. Operation of mechanism. The spring set contacts are shown in the upper dotted enclosure of Figs. 5, 5a, in association with an outgoing junction relay set, the lower dotted enclosure showing contacts of the timing device described in Application No. 20816 of 1954. At the initiation of a call relays A and B respond to prepare a circuit for dialling relay CO. Relays MD and BA respond with B and MC responds with BA which also energizes magnet FCM in the timing device. Contacts FC, however, do not operate until permitted to do so by a cam in the device. Relay MC in operating energizes magnet DGM, magnet 27 of Fig. 1, to unlock the sun and planet gear held by pin 30. A relay HA, not shown, also operates when the relay set is seized and extends the line to a distant exchange. If it is desired to charge for a call by operating the meter six times for the first 3 minutes and twice for each subsequent minute, it is arranged that the first dialled digit is 6 so that, as relay A responds to each pulse, relay CD holds back during the digit train while the right hand winding DM is pulsed six times to step the mechanism, cam 19 moving 72 degrees clockwise and cams 21 and 22 moving 72 degrees counter-clockwise, as shown in Fig. 4, contacts ON and MF being operated. At the end of the digit train CD falls back and as contacts ON have removed an earth from MC, MC falls back to disconnect DM from the impulsing circuit of relay A and to de-energize DGM, thereby relocking planet-wheel 24 which has remained fixed with its associated cam 26. Provision may be made by means of an additional cam with spring contacts in an associated counting circuit to check the number of pulses initially received against the number produced. Further digits are dialled over the junction and when the call is answered relay D responds over retard coil RA, releasing MD and energizing DD to reverse battery on the incoming line. A relay DL, not shown, also responds, remaining energized for the duration of the call and connecting a source of one-second pulses on lead x to a cam driving magnet CTM of the timing device. After a grace period of 12 seconds contacts TD1 operate and connect earth to the windings DM connected in parallel so that the magnet interacts as described in Specification 462,773 to step the mechanism at a predetermined rate. At the first step, as planet-wheel 24 is locked, contacts MON operate, so that at each step contacts DM connect meter battery to the private wire P. In this operation cam 21 is stepped clockwise and when it regains its initial position after 6 steps spring set MF is released and locked up independently of cam 21 by magnet MFM which was energized as soon as cam 26 moved off normal to operate contacts MON. The meter batterv is disconnected when contacts MF are released and DM continues to step until cam 26 reoperates contacts MON to disconnect the self-stepping circuit and the magnet MF. After a further 13 seconds contacts FC are operated by a cam in the timing device and lock-up to change the meter battery circuit to contacts SF controlled by cam 22 of the mechanism. At the end of 2.8 minutes contacts PP1 close to connect pip-pip tone to the line and at 3 minutes contacts RC1 operate to reconnect the self-stepping circuit of magnet DM, MFM being energized on the first step. Contacts SF are operated, as shown by the contour of cam 22 in Fig. 4, and apply meter battery to the private wire twice before cam 21 restores and locks up contacts MF. The mechanism steps through the remainder of a revolution until cam 26 restores contacts MON. Contacts RC1 of the timing device operate at one-minute intervals to repeat metering for as long as the call lasts. When the call is terminated relays A, B, BA, D, DD, HA, and DL release; DL completing a self-stepping circuit for motor magnet CTM of the timing device which homes until broken by off-normal contacts N. The magnet DGM is de-energized over contacts ON when BA releases to release the planet-wheel 24 and magnet DM self-steps to return cams 19 and 21 counter-clockwise and clockwise, respectively, until cam 19 restores contacts ON when the mechanism is restored to normal. In place of a single step-by-step motor and a reversing gear two step-by-step motors driving in different directions may be used with appropriate switching between the two.